Authenticated (28/09/07) by Eline Deirdre Lorenzen, Institute of Biology, University of Copenhagen.
http://www.bi.ku.dk/staff/person.asp?ID=388
Interbreeding: Cross-breeding with a different species or subspecies.
Morphological: Referring to the visible or measurable characteristics of an organism and their function.
Subspecies: A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.